.NET

Dynamic Server Controls & INamingContainer

Michael Cook — Thu, 17 Mar 2005 00:50:00 GMT

It turns out that creating a custom server control that uses dynamic controls (controls added at runtime) is a huge pain in the ass. Add to that INamingContainer, which is virtually a necessity when making a composite control (it lets you have more than one copy of the server control on the page by guaranteeing that the child controls have unique id's) completely screws around with control's life-cycle, and you have one frustrated developer..

It's taken me entirely too long to create my data-paging server control, which simply creates the buttons you need to page through data (First, Prev, 1, 2, 3, Next, Last - etc) and provides an event for when the user clicks a button. It doesn't do the actual data-paging, just the controls so it should have been a simple control to write. Nope, I had to try just about every trick and lame technique in the book to get it to work the way I want. Along the way I tried such things as serializing out the settings to a hidden field (essentially creating my own custom viewstate), so that I could re-instantiate my controls before the events are supposed to fire. Turns out that way doesn't work so hot if you need to hide the control for whatever reason (hidden panel, etc), since the hidden field won't get included in the page. I also tried to tap into virtually every part of the control's life-cycle, which ultimately useless, turned out to be good for learning how things worked, inserting hidden fields, or creating and re-creating controls at different points.

Finally I have something that works, though it's not without it's share of shortcuts. I ultimately borrowed some idea and code from Dennis Bauer's DynamicControlsPlaceHolder, to re-create my dynamic controls out of the viewstate on a postback. The downside to this technique is that it doesn't re-wire the events properly, and even worse, you loose command arguments (which is what I used to determine which page button the user clicked on). So I had to work around that by storing some extra info into the persistenceString (a string that is passed along that tracks which controls to restore).

So once the control is loaded, I override CreateChildControls to create the final controls the user sees. I do this by calling this.Controls.Clear() to wipe out the controls that were created by from the viewstate (which could be different depending on which page the user clicked on). It's not great, but it's much easier and probably faster than comparing the new controls that will be generated to the existing ones and adding or removing ones that don't match up.

It would be nice if there was some way to detect which button was clicked so I could only restore that control to capture the event, but I don't know if that's possible. So it now works with only instantiating the controls a maximum of twice per page load, which is an improvement over earlier versions.

All of the leaves my final workaround for INamingContainer. As mentioned above using INamingContainer causes the control life-cycle events to be called in a different order. This meant that my CreateChildControls was being called after my event was firing, the event which set the current page that the CreateChildControls relied upon. That was a problem. I could have forced a call to re-create the child controls after my event fired, but that would be adding a lot of overhead to an already inefficient system by having to re-create the controls 3 times instead of two.

So I ended up manually setting all of the control id's so that they used the parent control's ClientID. This was essentially what INamingContainer did, sans the odd life-cycle changes. It wasn't as big a deal as it could have been since I had to explicitly set the control id's for the DynamicControlsPlaceHolder code to work anyway.

It's not pretty, but it works. I can put as many pagingcontrols on a page as I want (say at the top and bottom of a repeater), even hide them and it all works. I can't imagine having to do anything more complex with dynamic controls in a server since this one was such a pain. On the upside I learned many of the finer points of creating server controls and the next one I write should go a little more smoothly.

How to Integrate .Text and FreeTextBox 3.0

Michael Cook — Wed, 23 Feb 2005 10:48:00 GMT

Brendan Tompkins has written up some instructions on how to modify your .Text 0.95 to use FreeTextBox 3.0.
I'll have to check it out and see how it differs from my implementation (which probably isn't the greatest).

Coding Guidelines

Michael Cook — Tue, 15 Feb 2005 04:24:00 GMT

Brad Abrams has given us a taste of Microsoft by showing us their internal coding guidelines. There are some interesting things, and overall it answers a lot of questions that new developers my face. For the record here are my personal coding habits, which by default are my companies coding standards.

namespace Company.Product.Component {

public class Test {

private int _myInt;
private string _myString;

    public int MyInt {
      get { return _myInt; }
      set { _myInt = value; }
}

public string MyString {
      get { return _myString; }
      set { _myString = value; }
    }

public Test() {
}

    public void MethodA(string myArgument) {
      _myString = myArgument;
    }

    private void MethodB() {
      //Do Something Here
    }

}
}

I consider this style a work in progress, and I'm always tweaking things as I find better or new ways to do things but overall it works pretty well. The code uses 2 spaces for an indent and no tabs, unless it's html/xml. Private members use the '_' prefix because 'm_' is just too much and only using casing to distinguish between variables is a bad practice that will get you in trouble if you ever work in a case insensitive language like VB.net.

Optional braces are always required, all if statements, no matter how simple must have braces and this includes switch statements as well (which I guess is pretty rare).

There are, however, a few things that I haven't quite nailed down yet, the worst offender being asp.net control names. Right now I'm using a quasi-post-fix-hungarian sort of thing by appending the control type to the name ala nameTextBox, userRepeater, etc. This is very clunky, but prevent naming collisions where you could have a control, a private member, and a local variable all with the same or similar names. Of course I wrap my asp.net controls in a nice member variable to make things simpler. If anyone has a better naming scheme I'd love to here about it.

Custom .Text 0.95 Build and Upgrading to 0.96

Michael Cook — Thu, 03 Feb 2005 15:03:00 GMT

Since I switched over to Firefox a couple of months ago, it's been more and more painful to switch back to IE just to get the nice FreeTextBox controls to update my blog. FreeTextBox (irononically not entirely free anymore) has supported non-IE browsers for a while now, but .Text was built against an early version. So I grabbed the source code for .Text 0.95 from gotdotnet, which is the last version publically released from Scott Watermasysk, since he rolled .Text into Telligent Systems' Community Server (which has a lot more features, but may or may not have a more restrictive liscense, which is perhaps why so many people are interested in maintaining .Text).

Except it isn't the last version. At some point in time before Community Server, Scott was working on .Text 0.96 and even got it to the point where several sites were using it in some form (apparently as long as a year ago). The problem is the source was never officially released... or was it? If you follow the directions from Dave Burke you can get yourself a copy of .Text 0.96 from SourceGear's public vault. Is this an official release? A silent release to appease frustrated developers? No one seems to know.

If you do download the code, chances are it won't work right off the bat. The code has some build errors in it, and so far I haven't been able to get it to run. Which is why I am currently running 0.95 with FreeTextBox 3.0 hacked into it, but it seems to work pretty well so far. If you do get it running and want to migrate your existing 0.95 database, Chee Wee has some 0.96 upgrade instructions for you.

Fix for the Broken VS Wizards

Michael Cook — Mon, 29 Nov 2004 14:53:00 GMT

I posted this Visual Studio error the other day, which shows up when you uninstall a VS add-in that tries to take a few critical dll's with it (which seems to be about half of the add-ins I've tried). Pete Davis explains what to you can do to try to fix this problem, without reinstalling all of Visual Studio.

I should point out one minor difference I noticed. In my copy of Visual Studio 2003, extensibility.dll and VSLangProj.dll were both located in C:\Program Files\Microsoft Visual Studio .NET 2003\Common7\IDE\PublicAssemblies rather than C:\Program Files\Microsoft Visual Studio .NET 2003\Common7\IDE\.

If you suck at writing Visual Studio plugins...

Michael Cook — Wed, 24 Nov 2004 20:46:00 GMT

...Please stop. Now. I'm really tired of dealing with

when I uninstall your crappy add-in.

Thanks.

Amazon Web Services and .NET

Michael Cook — Tue, 09 Nov 2004 15:26:00 GMT

Thanks to my new phone I am now a web surfing fool (or perhaps just a regular fool). However I've had one problem... I can't surf Amazon.com too well. While I occasionaly shop at Amazon.com I usually perfer to use it as a research tool too look up reviews of products I'm interested in, or just sometimes price compare. But I've not had much luck so far on my phone. The main site is too design heavy and slow to be practical on a phone. The PDA version doesn't render correctly on mobile explorer for some reason and the phone version is just way to limited and doesn't give me the information I want.

So I thought I would make my own version with the help of Amazon Web Services aka E-Commerce Service (ECS). I fired up VS and grabbed the latest WDSL. I checked the docs and built a simple wrapper for a basic search:

public static Item[] Search( string keywords) {

AWSECommerceService service = new AWSECommerceService();

ItemSearchRequest request = new ItemSearchRequest();

request.Power = "title:" + keywords;

request.SearchIndex = "Books";

request.ResponseGroup = new string[] { "Small" };

request.Sort = "salesrank";

ItemSearchRequest[] requests = new ItemSearchRequest[] {

request };

ItemSearch search = new ItemSearch();

search.AssociateTag = "myassociatetag-20";

search.SubscriptionId = Globals.AWSID;

search.Request = requests;

try {

ItemSearchResponse response = service.ItemSearch( search );

Items info = response.Items[ 0 ];

return info.Item;

}

catch (Exception ex) {

Console.WriteLine( ex.ToString() );

}

return null;

}

Btw, this article helped get me going. Everything looked great and I built a demo app to try it out. I immediately ran into a problem. It turns out that the WDSL provided by Amazon or the code generated but .NET has a few problems with it. These led me to some wonderful and cryptic error messages like:

An unhandled exception of type 'System.InvalidOperationException' occurred in system.web.services.dll
Additional information: Method AWSECommerceService.CustomerContentSearch can not be reflected.

and

Types CustomerReviews1 and CustomerReviews both use the XML type name, CustomerReviews, from namespace http://webservices.amazon.com/AWSECommerceService/2004-10-19. Use XML attributes to specify a unique XML name and/or namespace for the type.

or even

File or assembly name s5plrkv5.dll, or one of its dependencies, was not found.

After a bit of research I came across this helpful post on the official Amazon.com Web Services discussion board which explains how to fix the issues I was having:

Workaround:

Double click on "Web References" in your VS.NET solution.
Double click on the "WebReference" object and the Object Browser window should open up.
In the Object Browser window’s left pane, double click on the object with the same name as your application. This should expand the list tree. Double click on the .WebReference object and this should expand to a list of objects starting with "AccessoriesAccessory".
In this list of objects, double click on AWSECommerceService. This should open up the source code file that VS.NET generates when it parses the WSDL. Search for "public class CustomerReviews1". You should see the following lines of code.

[System.Xml.Serialization.XmlTypeAttribute(TypeName="CustomerReviews", Namespace="http://webservices.amazon.com/AWSECommerceService/2004-10-19")]

public class CustomerReviews1 {
Replace the TypeName="CustomerReviews" with TypeName="CustomerReviews1".
Save this file.

Dependencies not found issue:

On running your application, Microsoft’s runtime framework will display the following error.

"Server Error in /XXX Application
File or Assembly name yyy.dll, or one of its dependencies, was not found."

(The name of the file (yyy) is not fixed and will vary for every execution run.)

Workaround:

Follow the instructions above to open the AWSECommerceService class generated by VS.NET.
Search for "public string[][] Request;". You should see the following lines of code.

[System.Xml.Serialization.XmlArrayItemAttribute("BrowseNodeId", typeof(string), IsNullable=false)]
public string[][] Request;
Modify these lines to

[System.Xml.Serialization.XmlArrayItemAttribute("BrowseNodeId", IsNullable=false)]
public string[] Request;
Save this file.

Thanks to those tips (I never would have figured it out myself) I was able to get the search tool for my app up and running.

Microsoft .NET 1.1 Service Pack 1

Michael Cook — Wed, 01 Sep 2004 12:13:00 GMT

Though it is available as part of Windows XP service Pack 2 Reail CD, you can download the Microsoft Framework 1.1 Service Pack 1 separately if you are so inclined.

Thanks again Scott.

Avalon for Windows XP?

Michael Cook — Wed, 01 Sep 2004 12:08:00 GMT

Ian Griffiths points out that Microsoft is planning on releasing their new gui code-named Avalon along with the rest of WinFX to Windows XP and Windows 2003 users.

I find it an odd strategy by Microsoft since those are the core elements of what makes Longhorn interesting to me as a user and a developer. But the faster these new technologies spread the sooner I can use and develop for them.

ASP.NET Default "Enter" Button

Michael Cook — Tue, 31 Aug 2004 11:51:00 GMT

Scott Hanselman posted a tip he found on Developer.com on how to set the default button to trigger when hitting the enter key on a web form:

Imagine you've created an ASP.NET Web page with a search button. The user taps a phrase into a text box and presses Enter. On most regular Web pages (think: Google), the form would be submitted and the results returned. In other words, the search button is automatically "clicked" for you.

However on an ASP.NET Web page, pressing Enter resubmits the form to the server, but actually does nothing... which is pretty useless, really.

So, how do you set a default button to be clicked when the user presses Enter? Simply add the following line to your page's Load event, replacing "btnSearch" with the name of your button. It uses a hidden Page method called RegisterHiddenField and works splendidly:
Page.RegisterHiddenField("__EVENTTARGET", "btnSearch")

There are also some more good ideas and reccomendations in the comments section.

Edit: Scott has posted a summary of the best suggestions and a new one from Dino Esposito.